Semiconductor devices including compounds such as GaN, AlGaN, and the like have many advantages such as wide and easily adjustable bandgap energy and the like, and can be variously used as light emitting devices, light receiving devices, various diodes, and the like.
Particularly, a light emitting device such as a light emitting diode or a laser diode using a Group III-V or II-VI compound semiconductor material may realize various colors, such as red light, green light, blue light, an ultraviolet light, and the like, resulting from development of a thin film growth technique and a device material, realize white light with high efficiency using a phosphor or by combining colors, and has advantages of low power consumption, a semi-permanent lifetime, a fast response time, safety, and environment friendliness when compared to conventional light sources such as fluorescent lamps and incandescent lamps.
In addition, when a light receiving device such as a photodetector or a solar cell is manufactured using a Group III-V or II-VI compound semiconductor material, due to development of an element material, the light receiving element absorbs light of various wavelength regions to generate a photoelectric current so that light in various wavelength regions from gamma rays to a radio wavelength region may be used. Further, with advantages of a fast response speed, safety, environmental friendliness, and easy control of a device material, the light device can also be easily used for power control, a microwave circuit, or a communication module.
Accordingly, application of the semiconductor device has expanded to a transmission module of an optical communication device, a light emitting diode (LED) backlight replacing a cold cathode fluorescent lamp (CCFL) that configures a backlight of a liquid crystal display (LCD) device, a white LED lighting device capable of replacing a fluorescent lamp or an incandescent lamp, a headlight of a vehicle, traffic lights, a sensor for detecting gas or fire, and the like. In addition, the application of the semiconductor device may be expanded to a high frequency application circuit, another power control device, and a communication module.
Particularly, a light emitting device emitting light in an ultraviolet wavelength region can be used for a hardening process and for curing, medical, and germicidal applications due to a bactericidal action.
Recently, research on ultraviolet light emitting devices has been actively carried out, but there is a problem that it is difficult to implement a vertical type ultraviolet light emitting device and crystallinity is degraded in the process of separating a substrate.
In a conventional semiconductor device, a strain can be varied in each semiconductor layer due to a lattice mismatch and a difference in thermal expansion coefficient between the semiconductor layers. The strain variation may cause dislocation or a defect in the semiconductor layer. The dislocation or defect may cause V-pits or cracks, and the V-pits or cracks may generate a leakage current.